Copper indium diselenide (CuInSe2, or CIS) and its higher band gap variants copper indium gallium diselenide (Cu(In,Ga)Se2, or CIGS), copper indium aluminum diselenide (Cu(In,Al)Se2), copper indium gallium aluminum diselenide (Cu(In,Ga,Al)Se2) and any of these compounds with sulfur replacing some of the selenium represent a group of materials, referred to as copper indium selenide CIS based alloys, have desirable properties for use as the absorber layer in thin-film solar cells. To function as a solar absorber layer, these materials should be p-type semiconductors. This may be accomplished by establishing a slight deficiency in copper, while maintaining a chalcopyrite crystalline structure. In CIGS, gallium usually replaces 20% to 30% of the normal indium content to raise the band gap; however, there are significant and useful variations outside of this range. If gallium is replaced by aluminum, smaller amounts of aluminum are used to achieve the same band gap.
Sputtering techniques may be used for deposition of CIS based alloy layers, and one component of such sputtering techniques is a sputtering target. The combination of soft metal elements such as In and Ga along with harder metals such as copper and aluminum into a single sputtering target presents multiple challenges due to the presence of intermetallic phases, and there exists a need in the art to develop inexpensive techniques that can successfully combine such elements together into reliable sputtering target assemblies.